1. Field of the Invention
The present invention relates to an electric circuit arrangement for controlling a power switching element associated with an electric motor used to adjust a motor vehicle unit in which one of two inputs of the power switching element is connected to the positive pole of a power supply and the other input is connectable to the negative pole of the power supply by (a) a first transistor controlled by a controller via a manually actuated switch and (b) a second transistor directly controlled by the switch.
2. Background Art
Electric circuit arrangements are used to control electrically operated motor vehicle units such as window and sliding roof adjustment systems which are driven by electric motors. That is, the circuit arrangements control the electric motors associated with motor vehicle units in order to control the movement of the motor vehicle units. The circuit arrangements typically control the motor vehicle units in accordance with specification and regulatory requirements. Certain of these requirements require motor vehicle units to have an emergency opening mode in case of circuit arrangement malfunction. Circuit arrangements malfunction, for example, as a result of short circuiting due to contact with salt water.
The emergency opening mode of a motor vehicle unit comes into play when the motor vehicle is submerged in water such as a lake or an ocean as a result of an accident. The water may be deep enough such that the passengers of the motor vehicle have to escape through windows or a sliding roof of the motor vehicle. As such, the electric motors associated with the motor vehicle units still have to be controllable to open their associated motor vehicle units when, for example, elements of the circuit arrangements are short-circuited as a result of being submerged in water or salt water.
Commonly assigned U.S. Pat. No. 6,559,614 discloses an electric circuit arrangement for controlling a motor vehicle unit. This circuit arrangement uses mechanical changeover switches as manually actuated switches which allow selective connections of the same circuit node to different voltages. However, such switches are technically complicated and, as a result, are susceptible to malfunction because of their complexity.